Communications services on communication networks are continuously becoming cheaper, faster, and easier to use, and are enabling myriads of new, important applications. Data sharing is one of them. As the performance of communication networks improves, more users, both individuals and institutions, resort to communication networks to share data with others. Over communication networks, users can now share multi-gigabyte videos in a matter of minutes; users can exchange real-time messages from all around the world using an instant messenger program; and users can share documents with others almost instantaneously. Communication networks have shaped and modified the way users communicate with others.
As users became accustomed to using communication services over a communication network, users have become more receptive to sharing confidential and private data over public networks as well. One popular communication medium for this purpose is E-mail. E-mails can carry confidential messages and important documents almost instantaneously, and can reduce the burden of printing hard copies and sending them via expensive and slow mail services. Unfortunately, although the E-mail system provides an easy way to share information, the E-mail system fails to provide the level of security desired in many scenarios. For example, financial professionals need to share confidential client information securely; lawyers need to send confidential legal documents to clients; human resources personnel need to share private employee data upon request; and medical professionals need to discuss patient health information with other medical professionals, potentially located off-site. Such confidential information should not be revealed to anyone else but the desired recipient, and the E-mail system as it currently stands does not guarantee that. In fact, an E-mail can be eavesdropped during transfer over public communication networks, and once the E-mail is eavesdropped, the content of the E-mail can be readily viewed by the intruder. Furthermore, anything that is stored on the E-mail server can also be readily accessed by the E-mail service provider. E-mail is not a secure medium for sharing confidential information.
Another popular mechanism for data sharing is a web folder. Some web services provide users with password-protected folders accessible via the web. Using this service, users can store data in a password-protected folder and send the password for the folder to targeted recipients, often using a separate communication medium such as E-mail. The password recipient can, in turn, access the folder using the received password and retrieve the stored data. These web folders can store large files, so they are especially useful for sharing large amounts of information. However, the web folder services are often not user-friendly and are not scalable when many users want to share multiple files. Every time a user wants to share information with another user, the user has to (1) make a password-protected folder for the recipient, (2) store the information in the folder, and (3) send the password for the folder over a communication medium to the recipient. Although this work flow can be manageable for sharing information with a small number of people, this work flow can quickly grow out of hand if a user wants to share information with a large number of people. Web folder services are also not secure enough for many applications. If a third party eavesdrops on the password, then the third party can easily access the information stored in the folder. Furthermore, anything stored in the service provider's server can be readily accessed by the service provider. Therefore, a web folder service is also not suitable for sharing confidential information in a scalable manner.